Applying mapping profile - Item - selected fields with transformation provided

Purpose
This story addresses exporting selected fields from the item records. It assumes that each requested field has the transformation field populated.

Scenario:
Given: the mapping profile contains selected fields and for each selected field the transformation is provided
When: the record is generated on the fly during the export
Then:

1. Only fields selected in the mapping profile are part of the exported record
2. The fields are populated with the data coming inventory item record according to transformations specified in the mapping profile
3. .mrc file is generated
4. Unit and API tests are written